Potentiometer construction



Sept. 2l, 1965 H. B. ENos ETAL 3,208,024

POTENTIOMETER CONSTRUCTION K Filed Dec. 5, 1962 020262/ Q www u um N /Zf2 /5 Z4 25 Z6 INVENTOR 420m LFA/0S,

Olf/ M ATTORNEY United States Patent 3,208,024 POTENTIOMETERCONSTRUCTION Harold B. Enos, Whittier, and Byron L. Hartley, Monrovia,Calif., assignors to Edcliff Instruments, Incorporated, Monrovia,Calif., a corporation of California Filed Dec. 5, 1962, Ser. No. 242,44219 Claims. (Cl. 338-162) The present invention relates to constructionof potentiometers.

Features of the subject invention provide a novel and simplifiedconstruction for the entire mechanical portion of subminiature, rotary,trimming potentiometers, permitting the application of new and improvedmanufacturing methods to such constructions with the result beingimproved usefulness, greater functional reliability and reducedmanufacturing costs. Other features of the present invention involve aconstruction wherein there is provided a high ratio driving means,improved contacting wiper means spring-loaded in a novel manner, withthe driving means comprising also a slip clutch acting as such at thelimits of travel of the wiper means.

It is therefore a general object of the present invention to provide animproved potentiometer construction embodying the above-indicatedfeatures.

A specific object of the present invention is to provide a constructionwhich may be made small and inexpensively.

Another specific object of the present invention is to provide animproved potentiometer construction permitting the use of simplemanufacturing methods in fabrication and assembly of the various parts.

Another specific object of the present invention is to provide apotentiometer construction incorporating novel high ratio driving means.

`Another specific object of the present invention is to provide a newpotentiometer construction involving novel wiper means which arespring-loaded.

Another specific object of the present invention is to provide animproved potentiometer construction using a novel slip clutchconstruction.

The features of the present invention which are believed to be novel areset forth with particularly in the appended claims. This inventionitself, both as to its organization and manner of operation, togetherwith further objects and advantages thereof, may be best understood byreference to the following description taken in connection with theaccompanying drawings in which:

FIGURE 1 is an elevational view showing the top of a potentiometerembodying features of the present invention.

FIGURE 2 is a view in side elevation of the same.

FIGURE 3 is a sectional view taken generally along the line 3 3 ofFIGURE l.

FIGURES 4, 5 and 6 are generally sectional views taken alongcorresponding lines 4-4, 5 5 and 6-6 in FIGURE 3.

FIGURE 7 shows a modified construction.

FIGURE 8 shows another modified construction.

FIGURE 9 is a sectional view taken generally along the line 9-9 ofFIGURE 8; and

FIGURE 10 illustrates still another modified construction.

Referring to FIGURES 1-6, the housing for the potentiometer comprisestwo parts 10 and 11, the part 10 for convenience being referred to asthe top part and the part 11 for convenience being referred to as thebottom part. The top part 10 has an internal peripheral shoulderedportion 10A against which the upper edge of the lower part 11 abuts, andafter assembly of the parts within the housing 10, 11, the same aresealed together by a sealant 12 which is disposed within a peripheralgrooved Patented Sept. 21, 1965 ice portion 13 defined by an inner wallof part 10 and an undercut part of part 11.

The bottom part or base 11 is formed to provide a peripheral shelfportion 15 on which the circular resistance element 16 rests, theresistance element 16 comprising a plurality of turns of resistance wirewound on a circular insulating form 17 With the ends of the resistanceelement 16 being connected as, for example, by soldering to the twoflexible insulated conductors 20 and 21 which extend through spacedsealed openings in the base member 11, these openings being sealed bythe same sealant 12.

The base portion 11 is formed also with an internally shouldered hubportion 24 for receiving a circular metallic pin 25 having a conical end25A, the base of the pin 25 having soldered thereto an insulatedflexible lead 26 which, like the leads 20 and 21, extends through asealed opening in the base member 11.

Thus hub portion 24, as shown in FIGURE 5, has a small protuberance 24Awhich acts as a stop member for a rotatable element 30 in the form of aspring disc having a portion 30A thereof stamped therefrom to providethe stamped finger 30A for engagement with the stop member 24A.

This element 30 has its central portion apertured and deformed toprovide a bearing portion 30B seatable on the tapered pin end 25A.

This element 30, las shown in FIGURE 3, has a second finger stampedtherefrom, such finger 30C having its extremity bent to provide an areathereon contactable with the resistance element 16. This finger 30C maythus be considered to be the so-called wiper arm of the potentiometer.

This spring element 30, in the form of a disc, has its peripheralportion engageable with an internal peripheral protuberance 10B of thetop member 10, such peripheral portion 10B extending, however, less than360 degrees to allow placement of a driving-worm-type screw 35 which hasits threaded portion engageable with the spaced apertured portions 30Din spring member 30 to provide a driving connection therebetween.

The worm screw 35 is rotatably mounted in the top part 10, there beingprovided a small bore 10E therein receiving the small shaft portion 35A:of worm screw 35 and an aligned large bore 10F receiving the largershaft portion 35B. This worm screw element 35 is provided with aninternal lug 35C which is engageable with a bifurcated end of a spindle40 having a shouldered portion 40A, a grooved portion 40B and a kerf 40Cfor turning of the worm screw 35 by a screwdriver. This worm screw 35 issealed by the O-ring 42 which is disposed between the shaft end 35B andthe shouldered portion 40A and which is maintained in a stressedcondition by the assembly pin 44 extending through the housing part 10and the annular groove 40B.

The spring disc element 30, in this assembly, is thus maintained in astressed condition to at all times maintain good electrical contactbetween itself and the tapered pin end 25A and also to maintain theresilient finger or wiper arm 30C in good electrical contact with theresistance element 16 and also to assure a resilient mechanicalconnection between the aperture disc portions 30D and thread on wormscrew 35, the peripheral spacing of the apertured portions 30Dcorresponding to the pitch 0f the worm screw thread.

It will be seen that upon rotation of the spindle 40, the wiper arm offinger 30C may be rotated an angular distance slightly less than 360degrees corresponding to the angular extent of resistance element 16 asa result 'of the driving connection between the worm screw 35 and theapertured portions 30D. This driving connection, however, is interruptedautomatically when the tab 30A (FIGURE 5) of the element 30 engages thestop member 24A, this being so since the disc 30A is suiiicientlyresilient to be pressed downwardly to disengage the apertured portions30D from the worm screw thread upon further rotation of theworm screw35. Thereafter, upon reverse rotation of the worm screw 35, there isautomatic engagement of the apertured portions 30D and thread on theworm screw 35 to provide a driving connection.

In the modification shown in FIGURE 7, the top and bottom housing partsand 11 are constructed as previously described and in this instance thepin 125, corresponding to the pin 25 of FIGURE 3, has a rounded end onwhich is resiliently seated a different form of driven disc 130corresponding to the disc 30 of FIGURE 3.

The disc 130 is made of spring stock and has a resilient finger or wiperarm 130C stamped therefrom, the finger 130C being resilient andcontacting the resistance element 16. Instead of providing aperturedportions such as the apertured portions 30D in FIGURE 5, in FIGURE 7equally spaced peripheral protuberances for engagement with the wormscrew 35 are provided, such protuberances 130D being formed, forexample, by deforrning the disc member 130. Also, such disc member 130has struck therefrom, by means of a stamping operation, three equallyspaced circumferentially extending spring lingers 130E each having itsends curled slightly to provide contact area with an inner face ofhousing part 10 to thereby assure good electrical contact at all timesbetween the pin 125 and resistance element 16. Also, as described inFIGURE 4, the disc 130 is sufficiently resilient to allow theprotuberances 130D to be disengaged from the worm screw 35 at extremepositions of rotation of the wiper arm 130C.

In the modification shown in FIGURE 8, the base housing part 11 isconstructed as in the previous figures, and the upper housing part 110,corresponding to the housing part 10 of the previous figures, is nowprovided with an inner boss 110A which serves as a gearing member forthe modied driven disc member 230 which in this instance is of resilientinsulating material having a blind bore 230F for receiving the boss110A. The disc 230 is formed with equally spaced and circumferentiallyextending protuberances 230D engageable with the worm screw 35, theprotuberances 230D being spaced commensurately with the pitch of theworm screw thread. In this case the resilient wiper arm 230C of metal isa separate element having an arcuate portion, as shown in FIG- URE 8,inserted within a circular :opening in the disc member 230 whichreceives the reduced end portion of pin 225 such that good electricalcontact is established between the wiper arm 230C and the pin 225 whensuch pin 225 is inserted in such opening. The protuberance 230A on thedisc member 230 serves as a stop member, performing the same function asthe tab 30A in FIG- URE 5.

Here again, as in the previous ligures, the disc 230 is sufficientlyresilient to automatically disestablish a driving connection between theprotuberances 230D and the worm screw 35 when the wiper arm 230C ismoved to either one of its two extreme positions of rotation.

FIGURE 10 is a modification of FIGURE 9 and in this case the wiper arm330C, inserted within the disc member 330, extends completely around thepin 325 which in this instance may have its end either rounded ortapered as in the previous figures. The protuberance 330A serves as astop member.

While the resistance element 16 is shown as comprising a plurality ofturns of resistance wire, it will be appreciated by those skilled in theart that this resistance element may take other forms; for example,resistance element 16 may be in the form of a molded compositionresistor of similar shape or, for example, resistance element 16 may bein the form of a resistive film coated upon a nonconductive base formedin a similar shape.

In each of the arrangements shown in the drawings, the worm screw 35 maybe made of insulating material used iwith a spindle of insulatingmaterial; the worm screw 35 may be made of insulating material used witha spindle of conducting material; or the worm screw 35 may be made ofconducting material used with a spindle of insulating material.

In the arrangement shown in FIGURE 8, using a disc 230 of insulatingmaterial, the worn screw 35 and spindle may be of conducting materialseparately or as one piece, and the top portion may be of conductingmaterial.

In all arrangements shown, the worn screw and spindle, corresponding toworn screw 35 and spindle 40, may be in one piece of insulatingmaterial.

While the particular embodiments of the present invention have beenshown and described, it will be obvious to those skilled in the art thatchanges and modifications may be made without departing from thisinvention in its broader `aspects and, therefore, the aim in theappended claims is to cover all such changes and modifications as fallwithin the true spirit and scope of this invention.

We claim:

1. In a potentiometer construction, a generally resilient disc-shapedmember having circumferentially extending and spaced means thereon fordriving the same, a housing, a generally circular resistance elementmounted ooaxially with said element within said housing, electricalcontacting and conducting means carried on said member and contactingsaid element, means rotatably supporting said member in said housing,the last mentioned means including a conducting pin in said housingelectrically contacting said electrical contacting and conductive means,means producing relative rotation between said element and member, saidmeans comprising a worm screw rotatably mounted in said housing andhaving its thread engageable with said spaced means for driving saidmember, said worm screw and said pin being on opposite sides of saidmember with said resilient member being stressed between said worm screwand said pin to establish a driving connection between said member andsaid worm screw.

2. A construction as set forth in claim 1 in which said sbpaced meanscomprises apertured portions in said mem- 1 er.

3. A `construction as set forth in claim 1 in which said spaced meanscomprises protuberances on said member.

4. A construction as set forth in claim 1 including means for limitingthe movement of said member, said member being suiiiciently resilient tomove said spaced means out of driving engagement with said worm screw todisestablish the driving connection therebetween when the movement ofsaid member is limited by said limiting means.

5. A construction as set forth in claim 4 in which said contacting andconducting means is a resilient linger integrally formed with saidmember.

6. A construction as `set forth in claim ll in which said member hasintegrally formed resilient iingers engaging said housing to press saidmember into engagement with said pin.

7. A construction as set forth in claim l in which said housing has acircumferentially extending protuberence engaging said member to pressit into engagement with said pin.

8. A construction as set forth in claim 7 in which said member is ofmetal and engages said pin.

9. A construction las set forth in claim 7 in which said member is ofinsulating material, said contacting and conducting means being of metaland mounted on said member and contacting said pin.

10. A construction as set forth in claim 9 in which said contacting andconducting means is inserted in said in` sulating material and partiallyembraces said pin.

11. A construction as set forth in claim 9 in whichsaid contacting andconducting means is inserted in said insulating material and surrounds`said pin.

12. In a potentiometer construction, a two-piece, housing having a basepart and a top part, salti base partgliaM- ing an inner annular shelfportion, a circular resistance element resting on said shelf portion,said base part having a hub portion coaxial with said shelf portion, ametal pin in and extending out of said hub portion, electrical leadsconnected respectively to said resistance element and said pin .andextending through sealed openings in said base part, a generallydisc-shaped resilient member rotatably mounted on said pin and havingcircumferentially extending and spaced means thereon for driving thesame, a worm screw rotatably mounted in said top part and having itsthread engageable with said spaced means, said worm screw and said pinbeing on opposite sides of said member, said top part having acircumferentially extending protuberance engaging said member to urgethe same toward said pin, said member being resilient and resilientlypressing said spaced means against said worm screw to establish adriving connection between the same, and electrical contact meanscontacting said pin and ycarried by said member for engaging saidresistance element.

13. A construction as set forth in claim 12 in which said worm screw hasshaft portions on opposite ends thereof joumalled for rotation in saidtop part, a spindle having a screwdriver kerf and a grooved portion andmeans thereon for driving said worm screw, an O-ring squeezed betweensaid worm screw and said spindle, and a pin in said top part andextending through said grooved portion maintaining said O-ring squeezedbetween said worm screw and said spindle.

14. A construction as set forth in claim 12 in which said member hasintegrally formed resilient fingers pressed against said top part.

1S. A construction as set forth in claim 12 in which said top part hasan internal boss extending into the circular apertured portion of saidmember.

16. A construction as set forth in claim 12 in which said member is of ametal and said contact means comprises an integrally formed fingerthereof.

17. A construction .as set forth in claim 12 in which said member is ofinsulating material and said contact means is inserted therein.

18. A construction as set forth in claim 12 including means for limitingmovement of said member in one position thereof, and said member beingsuiiciently resilient to permit disestab'lishment of the drivingconnection between said worm screw and member at said position.

19. In a potentiometer construction, a resistance element, a one piecedriven rotatable means contacting said element, worm screw means fornormally driving said driven means, said one piece driven means beinginherently resilient and being resiliently pressed by its inherentresiliency against said worm screw means to establish a drivingconnection between said worm screw means and rotatable means, saidresilient means being suiciently resilient to disestablish said drivingconnection upon the transmission of more than a predetermined forcebetween said Worm screw means and rotatable means, a two-part housinghaving two parts, said resistance element, one-piece rotatable means,worm screw means all being within said two-part housing, an electricalcontacting and conducting pin having one of its ends seated in one ofsaid housing parts and rotatably supporting said one-piece rotatablemeans at the other one of its ends, the other of -said housing partscontacting said one-piece rotatable means to stress and press saidrotatable means in electrical contact with said pin to establish anelectrical connection between said pin and said resistance elementthrough said one-piece rotatable means, said one-piece rotatable meansbeing of electrically conducting material, and said worm screw meansbeing rotatably mounted in said other housing part.

References Cited by the Examiner UNITED STATES PATENTS 2,880,293 3/59Blanco 338-175 X 2,887,554 5/59 Smith et al 338-164 X 2,952,825 9/60Bourns 338-175 X 3,054,077 9/62 Mellor 338--175 3,059,200 10/62 Bamford338-180 3,099,810 7/ 63 Habereder 338-162 3,105,217 9/63 Ferrell et al338-174 0 RICHARD M. WOOD, Primary Examiner.

ANTHONY BARTIS, Examiner.

1. IN A POTENTIOMETER CONSTRUCTION, A GENERALLY RESILIENT DISC-SHAPEDMEMBER HAVING CIRCUMFERENTIALLY EXTENDING AND SPACED MEANS THEREON FORDRIVING THE SAME, A HOUSING, A GENERALLY CIRCULAR RESISTANCE ELEMENTMOUNTED COAXIALLY WITH SAID ELEMENT WITHIN SAID HOUSING, ELECTRICALCONTACTING AND CONDUCTING MEANS CARRIED ON SAID MEMBER AND CONTACTINGSAID ELEMENT, MEANS ROTATABLY SUPPORTING SAID MEMBER IN SAID HOUSING,THE LAST MENTIONED MEANS INCLUDING A CONDUCTING PIN IN SAID HOUSINGELECTRICALLY CONTACTING SAID ELECTRICAL CONTACTING AND CONDUCTIVE MEANS,MEANS PRODUCING RELATIVE ROTATION BETWEEN SAID ELEMENT AND MEMBER, SAIDMEANS COMPRISING A WORN SCREW ROTATABLY MOUNTED IN SAID HOUSING ANDHAVING ITS THREAD ENGAGEABLE WITH SAID SPACED MEANS FOR DRIVING SAIDMEMBER, SAID WORN SCREW AND SAID PIN BEING ON OPPOSITE SIDES OF SAIDMEMBER WITH SAID RESILIENT MEMBER BEING STRESSED BETWEEN SAID WORN SCREWAND SAID PIN TO ESTABLISH A DRIVING CONNECTION BETWEEN SAID MEMBER ANDSAID WORN SCREW.